(1) Field of the Invention
The present invention relates to a processor such as a DSP and a CPU, and more particularly to a processor suitable for performing signal processing for sounds, images and others.
(2) Description of the Related Art
With the development in multimedia technologies, processors are increasingly required to be capable of high-speed media processing represented by sound and image signal processing. As existing processors responding to such requirement, there exist Pentium (R)/ Pentium (R) III Pentium 4 (R) MMX/SSE/SSE2 and others produced by the Intel Corporation of the United States supporting SIMD (Single Instruction Multiple Data) instructions. Of them, MMX, for example, is capable of performing the same operations in one instruction on a maximum of eight integers stored in a 64-bit MMX register.
However, there is a problem that such existing processors do not fully satisfy a wide range of requirements concerning media processing.
For example, although capable of operating on multiple data elements in a single instruction and comparing multiple data elements in a single instruction, the existing processors cannot evaluate the results of such comparisons in a single instruction. For example, an existing processor is capable of comparing two data elements stored in 32-bit registers on a byte-by-byte basis, and setting comparison results to four flags. However, it cannot make a judgment on whether all values of these four flags are zero or not in one instruction. For this reason, the processor needs to read out all four flags and execute more than one instruction for judging whether all such values are zero or not. This requires a plurality of instructions for evaluating results every time a comparison is made against another set of pixel values when four pixel values are used as a unit of comparison, resulting in an increased number of instructions and therefore a decreased speed of image processing.